Ordering a Guinness in a martini glass will exasperate your bartender and garner some serious side-eye from the regulars, no doubt. But a mathematician is arguing that an oversized version of the glass this could be the best vessel to serve the creamy stout in: It allows the bubbles to settle faster, according to research published in the American Journal of Physics.
William Lee, a professor of industrial mathematics at the University of Huddersfield in England, is a beer connoisseur in his own right. He’s been studying beer bubbles for quite some time. But Guinness provides an interesting conundrum. If you’ve ever poured the perfect pint (or watched your barman), you know the bubbles sink, rather than float to the top. Guinness isn’t defying the laws of physics, though. Lee conducted some experiments and found it’s the glassware that influences the bubbles—sloped sides to be exact.
The bubbles are technically still rising relative to the liquid, but they appear to fall because of the current in the glass (known as “circulatory flow”). The typical Guinness glass is wider at the top. So as the beer fills the glass, it runs down the sides and rises from the middle of the glass. This forces the bubbles to gush up through the center of the glass and more to flow down the sides, like a fountain.
“People think that the Guinness glass is designed to optimize the settling time,” Lee said in a press release. “But now we have a better understanding of the theory behind it, we might be able to make an even better glass so that it settles faster. Unfortunately, the ideal shape would look like a giant cocktail glass!”